package DataStructure.LinkedList;

public class q21_merge_two_lists {
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        ListNode dummy = new ListNode(-1);
        ListNode cur = dummy; // ?

        while (list1 != null && list2 != null) {
            if (list1.val < list2.val) {
                cur.next = list1;
                list1 = list1.next;
                cur = cur.next;
            } else {
                cur.next = list2;
                list2 = list2.next;
                cur = cur.next;
            }
        }
        if (list1 != null) cur.next = list1;
        if (list2 != null) cur.next = list2;
        return dummy.next;
    }
}
